Involvement of glycative stress in diabetic nephropathy and effects of anti-glycation material Kuromoji (Lindera umbellate Thunb.)

Abstract

Objective: The purpose of this study is to investigate the effects of anti-glycation activity of kuromoji (Lindera umbellate Thunb.) extract (KE) on diabetic nephropathy. Methods: Using streptozotocin-induced diabetic rats (STZ rats) and spontaneously diabetic mice (db/db mice), glycative stress-related indicators and biochemical changes were investigated during continuous administration of KE, and the effects of KE on inflammatory response in renal tissue was compared between two animal models. Then, mouse macrophage cells (RAW264.7 cells) were used to investigate the effects of glycated substances on the inflammatory response. Results: KE suppressed the amount of inflammatory cytokines (TNF-α, IL-6) in the renal tissue of STZ rats and db/db mice. In STZ rats, KE suppressed the increase in renal weight and the amount of autoantibodies against N^ε-(Carboxymethyl)lysine (CML). In db/db mice, the elevation of serum total cholesterol was suppressed. Treatment of RAW264.7 cells with CML-HSA (human serum albumin) increased TNF-α production, while CML alone did not. Conclusion: KE is thought to suppress the development of inflammatory response in renal tissue by reducing glycative stress during diabetic conditions.